Spreading techniques for frequency-shift keying modulation

ABSTRACT

Various aspects described herein relate to distinguishing frequency shift keying (FSK) signals transmitted by each user of multiple users in a wireless communications system. One or more symbols for transmitting in an FSK-modulated signal can be obtained by a user. The one or more symbols can be encoded based on a tone location assignment corresponding to a unique spreading code associated with the user. Quadrature amplitude modulation (QAM) and/or phase-shift keying (PSK) can be performed over at least one tone associated with the encoded symbols. Each user can transmit the encoded symbols to a receiving entity, where the receiving entity can decode each symbol received from the plurality of users to produce a distinguishable symbol for each user based on the unique spreading codes associated with each user.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application for patent claims priority to ProvisionalApplication No. 62/277,305 entitled “SPREADING TECHNIQUES FORFREQUENCY-SHIFT KEYING MODULATION” filed Jan. 11, 2016, which isassigned to the assignee hereof and hereby expressly incorporated byreference herein.

BACKGROUND

The present disclosure relates generally to wireless communicationsystems, and more particularly, to spreading techniques forfrequency-shift keying (FSK) modulation.

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of a telecommunicationstandard is Long Term Evolution (LTE). LTE is a set of enhancements tothe Universal Mobile Telecommunications System (UMTS) mobile standardpromulgated by Third Generation Partnership Project (3GPP). Generally, awireless multiple-access communication system can simultaneously supportcommunication for multiple wireless terminals (e.g., user equipment(UE)), each of which can communicate with one or more base stations overdownlink or uplink resources.

FSK is a conventional frequency modulation scheme used in wirelesscommunication systems. FSK modulation is known to be power-efficient andto reduce interference between wireless devices. Therefore, for awireless network where wireless devices are battery limited (e.g.,internet-of-things, IoT, devices) and need to share the network withmany other wireless devices, FSK is a good candidate for those wirelessdevices to modulate their uplink signals. However, when there aremultiple wireless devices transmitting FSK-modulated signals to a basestation, it can be difficult for the base station to decode theFSK-modulated signals to a unique signal transmitted by each of thewireless devices. Therefore, it is desirable to have techniques tohandle the detection of multiple users (i.e., multi-user detection) in awireless communications system when FSK modulation is used.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In accordance with an aspect, the present disclosure provides for amethod of decoding FSK-modulated signals received from multiple users ina wireless communications system. The method includes receiving, via achannel, a first modulated symbol from a first user equipment (UE), thefirst modulated symbol being FSK modulated based on a first spreadingcode. The method further includes receiving, via the channel, a secondmodulated symbol from at least one second UE, the second modulatedsymbol being FSK modulated based on a second spreading code differentfrom the first spreading code. In addition, the method includesdecoding, based on the first spreading code and the second spreadingcode, each of the first modulated symbol and the second modulated symbolto produce a distinguishable symbol transmitted by each of the first UEand the at least one second UE.

In accordance with another aspect, the present disclosure provides anapparatus (e.g., a base station) for multi-user wireless communications,the apparatus including a transceiver, a memory configured to storeinstructions and one or more processors communicatively coupled toreceive, via the transceiver and a channel, a first modulated symbolfrom a first user equipment (UE), the first modulated symbol beingfrequency-shift keying (FSK) modulated based on a first spreading code,to receive, via the transceiver and the channel, a second modulatedsymbol from at least one second UE, the second modulated symbol beingFSK modulated based on a second spreading code different from the firstspreading code, and to decode, based on the first spreading code and thesecond spreading code, each of the first modulated symbol and the secondmodulated symbol to produce a distinguishable symbol transmitted by eachof the first UE and the at least one second UE.

In accordance with another aspect, the present disclosure provides anapparatus (e.g., a base station) for multi-user wireless communications.The apparatus includes means for receiving, via a channel, a firstmodulated symbol from a first user equipment (UE), the first modulatedsymbol being frequency-shift keying (FSK) modulated based on a firstspreading code. The apparatus further includes means for receiving, viathe channel, a second modulated symbol from at least one second UE, thesecond modulated symbol being FSK modulated based on a second spreadingcode different from the first spreading code. In addition, the apparatusincludes means for decoding, based on the first spreading code and thesecond spreading code, each of the first modulated symbol and the secondmodulated symbol to produce a distinguishable symbol transmitted by eachof the first UE and the at least one second UE.

In accordance with yet another aspect, the present disclosure provides acomputer-readable medium (e.g., a non-transitory medium) storing codeexecutable by a computer for multi-user wireless communications, thecode including code for receiving, via a channel, a first modulatedsymbol from a first user equipment (UE), the first modulated symbolbeing frequency-shift keying (FSK) modulated based on a first spreadingcode. The computer-readable medium may further include code forreceiving, via the channel, a second modulated symbol from at least onesecond UE, the second modulated symbol being FSK modulated based on asecond spreading code different from the first spreading code. Inaddition, the computer-readable medium may further include code fordecoding, based on the first spreading code and the second spreadingcode, each of the first modulated symbol and the second modulated symbolto produce a distinguishable symbol transmitted by each of the first UEand the at least one second UE.

In accordance with another aspect, the present disclosure provides for amethod of transmitting FSK-modulated signals in a multiple user wirelesscommunications system. The method includes identifying, at a first UE, afirst spreading code different from a second spreading code for at leastone second UE. The method further includes generating, by the first UE,at least one first modulated symbol by performing FSK modulation of atleast one first symbol based on the first spreading code. In addition,the method includes transmitting the at least one first modulated symbolto a base station, the base station being configured to produce, basedon the first spreading code, the at least one symbol for the first UEfrom the first modulated symbol distinguishable from at least one secondsymbol produced by the base station for the at least one second UE froma second modulated symbol transmitted by the at least one second UE.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of aspects describedherein, reference is now made to the accompanying drawings, in whichlike elements are referenced with like numerals. These drawings shouldnot be construed as limiting the present disclosure, but are intended tobe illustrative only.

FIG. 1 is a block diagram illustrating an example of a multi-userwireless communications system for distinguishing FSK-modulated signalsbetween users in accordance with aspects described herein.

FIG. 2 is a flow diagram representing an example method for transmittingFSK-modulated signals in a multi-user wireless communications system inaccordance with aspects described herein.

FIG. 3 is a diagram conceptually illustrating an example of a spreadingtechnique for distinguishing four FSK (4-FSK) signals between two usersin accordance with aspects described herein.

FIG. 4 is a diagram conceptually illustrating an example of a spreadingtechnique for distinguishing 4-FSK-modulated signals between four usersin accordance with aspects described herein.

FIG. 5 is a flow diagram representing an example method for decodingFSK-modulated signals in a multi-user wireless communications system inaccordance with aspects described herein.

FIG. 6 is a diagram conceptually illustrating an example of performingdecoding of FSK-modulated signals received from two users in accordancewith aspects described herein.

FIG. 7 is a block diagram illustrating an example two stage decoder fordecoding FSK and QAM/PSK modulated signals in a multi-user wirelesscommunications system in accordance with aspects described herein.

FIG. 8 is a diagram illustrating an example of an evolved Node B anduser equipment in a wireless communication network.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known components are shown in blockdiagram form in order to avoid obscuring such concepts. Moreover, in anaspect, a component may be generally understood to be one of the partsthat make up a system, may be hardware or software, and/or may bedivided into other components.

Described herein are various aspects related to distinguishingFSK-modulated signals transmitted by multiple users (e.g., multiple UEs)in a wireless communications system. For example, in an aspect, togenerate an FSK-modulated signal, data symbols can be encoded by a userin accordance with a tone location assignment corresponding to a uniquespreading code associated the user. Each of the plurality of users canthen transmit their respective FSK-modulated signal to a receivingentity (e.g., a base station). In an aspect, the receiving entity candecode the FSK-modulated signals received from the plurality of usersbased on the unique spreading codes associated with each user to producea distinguishable symbol transmitted by each of the users. In anotheraspect, quadrature amplitude modulation (QAM) and/or phase-shift keying(PSK) can be utilized to modulate tones of the FSK-modulated signalbefore transmitting the FSK-modulated signal to the receiving entity.

Referring to FIGS. 1-8, aspects are depicted with reference to one ormore components and one or more methods that may perform the actions orfunctions described herein. Although the operations described below inFIGS. 2 and 5 are presented in a particular order and/or as beingperformed by an example component, it should be understood that theordering of the actions and the components performing the actions may bevaried, depending on the implementation. Moreover, it should beunderstood that the following actions or functions may be performed by aspecially-programmed processor, a processor executingspecially-programmed software or computer-readable media, or by anyother combination of a hardware component and/or a software componentcapable of performing the described actions or functions.

FIG. 1 is a schematic diagram illustrating a system 100 for wirelesscommunication, according to an example configuration. System 100includes two transmitting entities (e.g., a first transmitting entity102-a and a second transmitting entity 102-b) that each transmit signalsto a receiving entity 104. In an example, the first transmitting entity102-a and the second transmitting entity 102-b may be, or may include atleast a portion of, a user equipment (UE) that transmits signals toreceiving entity 104, which may be, or may include at least a portionof, a base station, to access a wireless network. The first transmittingentity 102-a and the second transmitting entity 102-b may be stationaryor mobile. Thus, in one example, first transmitting entity 102-a andreceiving entity 104 may have established one or more channels overwhich to communicate via one or more signals 109-a, which can betransmitted by transmitting entity 102-a (e.g., via transceiver 106) andreceived by receiving entity 104 (e.g., via transceiver 156). Similarly,second transmitting entity 102-b and receiving entity 104 may haveestablished one or more channels over which to communicate via one ormore signals 109-b. In addition, though two transmitting entities 102-aand 102-b and one receiving entity 104 are shown, it is to beappreciated that more than two transmitting entities 102-a (as shown)can communicate with a receiving entity 104, a transmitting entity 102-acan communicate with multiple receiving entities 104, and/or the like.In addition, it is to be appreciated that receiving entity 104 may alsoinclude the components for performing the functions of transmittingentity 102-a described below for transmitting communications, in oneexample.

In an aspect, transmitting entity 102-a may include one or moreprocessors 103 and/or a memory 105 that may be communicatively coupled,e.g., via one or more buses 107, and may operate in conjunction with orotherwise implement a communicating component 110 for managingcommunications, including uplink communications of FSK-modulatedsignals, with receiving entity 104. For example, the various operationsrelated to communicating component 110 may be implemented or otherwiseexecuted by one or more processors 103 and, in an aspect, can beexecuted by a single processor, while in other aspects, different onesof the operations may be executed by a combination of two or moredifferent processors. For example, in an aspect, the one or moreprocessors 103 may include any one or any combination of a modemprocessor, or a baseband processor, or a digital signal processor, or anapplication specific integrated circuit (ASIC), or a transmit processor,receive processor, or a transceiver processor associated withtransceiver 106. Further, for example, the memory 105 may be anon-transitory computer-readable medium that includes, but is notlimited to, random access memory (RAM), read only memory (ROM),programmable ROM (PROM), erasable PROM (EPROM), electrically erasablePROM (EEPROM), a magnetic storage device (e.g., hard disk, floppy disk,magnetic strip), an optical disk (e.g., compact disk (CD), digitalversatile disk (DVD)), a smart card, a flash memory device (e.g., card,stick, key drive), a register, a removable disk, and any other suitablemedium for storing software and/or computer-readable code orinstructions that may be accessed and read by a computer or one or moreprocessors 103. Moreover, memory 105 or computer-readable storage mediummay be resident in the one or more processors 103, external to the oneor more processors 103, distributed across multiple entities includingthe one or more processors 103, etc.

In particular, the one or more processors 103 and/or memory 105 mayexecute actions or operations defined by communicating component 110 orits subcomponents. For instance, the one or more processors 103 and/ormemory 105 may execute actions or operations defined by an input streamobtaining component 112 for obtaining an input stream of one or moresymbols for communicating to a receiving entity 104. In an aspect, forexample, input stream obtaining component 112 may include hardware(e.g., one or more processor modules of the one or more processors 103)and/or computer-readable code or instructions stored in memory 105 andexecutable by at least one of the one or more processors 103 to performthe input stream obtaining operations described herein.

Further, for instance, the one or more processors 103 and/or memory 105may execute actions or operations defined by a spreading codedetermining component 114 for determining a spreading code that definestone locations for use in FSK modulating of the input stream of symbols.In an aspect, for example, spreading code determining component 114 mayinclude hardware (e.g., one or more processor modules of the one or moreprocessors 103) and/or computer-readable code or instructions stored inmemory 105 and executable by at least one of the one or more processors103 to perform the spreading code determining operations describedherein.

Further, for instance, the one or more processors 103 and/or memory 105may execute actions or operations defined by a waveform generatingcomponent 116 for generating a waveform for transmitting a signal to thereceiving entity 104 based on a spreading code. In an aspect, forexample, waveform generating component 116 may include hardware (e.g.,one or more processor modules of the one or more processors 103) and/orcomputer-readable code or instructions stored in memory 105 andexecutable by at least one of the one or more processors 103 to performthe waveform generating operations described herein.

Further, for instance, the one or more processors 103 and/or memory 105may execute actions or operations defined by a FSK encoding component118 for modulating (e.g., encoding) the input stream of symbolsaccording to a spreading code. In an aspect, for example, FSK encodingcomponent 118 may include hardware (e.g., one or more processor modulesof the one or more processors 103) and/or computer-readable code orinstructions stored in memory 105 and executable by at least one of theone or more processors 103 to perform the FSK modulating operationsdescribed herein.

Further, for instance, the one or more processors 103 and/or memory 105may optionally execute actions or operations defined by a quadratureamplitude modulation/phase-shift keying (QAM/PSK) encoding component 130for performing QAM and/or PSK modulation (e.g., encoding) of tonesassociated with a modulated stream of symbols. In an aspect, forexample, QAM/PSK encoding component 130 may include hardware (e.g., oneor more processor modules of the one or more processors 103) and/orcomputer-readable code or instructions stored in memory 105 andexecutable by at least one of the one or more processors 103 to performthe QAM and/or PSK modulating operations described herein.

Similarly, in an aspect, receiving entity 104 may include one or moreprocessors 153 and/or a memory 155 that may be communicatively coupled,e.g., via one or more buses 157, and may operate in conjunction with orotherwise implement a communicating component 120 for managingcommunications with at least one transmitting entity (e.g., firsttransmitting entity 102-a). For example, the various functions relatedto communicating component 120 may be implemented or otherwise executedby one or more processors 153 and, in an aspect, can be executed by asingle processor, while in other aspects, different ones of thefunctions may be executed by a combination of two or more differentprocessors, as described above. It is to be appreciated, in one example,that the one or more processors 153 and/or memory 155 may be configuredas described in examples above with respect to the one or moreprocessors 103 and/or memory 105 of transmitting entity 102-a.

In an example, the one or more processors 153 and/or memory 155 mayexecute actions or operations defined by communicating component 120 orits subcomponents. For instance, the one or more processors 153 and/ormemory 155 may execute actions or operations defined by a data streamobtaining component 122 for obtaining a data stream from a signalreceived from transmitting entity 102-a, which can be provided to higherlayers for processing. In an aspect, for example, data stream obtainingcomponent 122 may include hardware (e.g., one or more processor modulesof the one or more processors 153) and/or computer-readable code orinstructions stored in memory 155 and executable by at least one of theone or more processors 153 to perform the data stream obtainingoperations described herein.

Further, for instance, the one or more processors 153 and/or memory 155may execute actions or operations defined by a FSK decoding component124 for performing decoding (e.g., demodulating) on a signal receivedfrom transmitting entity 102-a. In an aspect, for example, FSK decodingcomponent 124 may include hardware (e.g., one or more processor modulesof the one or more processors 153) and/or computer-readable code orinstructions stored in memory 155 and executable by at least one of theone or more processors 153 to perform the FSK decoding operationsdescribed herein.

Further, for instance, the one or more processors 153 and/or memory 155may optionally execute actions or operations defined by a QAM/PSKdecoding component 126 for performing decoding (e.g., demodulating) on asignal received from transmitting entity 102-a. In an aspect, forexample, QAM/PSK decoding component 126 may include hardware (e.g., oneor more processor modules of the one or more processors 153) and/orcomputer-readable code or instructions stored in memory 155 andexecutable by at least one of the one or more processors 153 to performthe QAM and/or PSK decoding operations described herein.

It is to be appreciated that transceivers 106, 156 may be configured totransmit and receive wireless signals through one or more antennas, aradio frequency (RF) front end, one or more transmitters, and one ormore receivers. In an aspect, transceivers 106, 156 may be tuned tooperate at specified frequencies such that transmitting entity 102-a andreceiving entity 104 can communicate at a certain frequency. In anaspect, the one or more processors 103 may configure transceiver 106and/or one or more processors 153 may configure transceiver 156 tooperate at a specified frequency and power level based on aconfiguration, a communication protocol, etc. to communicate signals109-a.

In an aspect, transceivers 106, 156 can operate in multiple bands (e.g.,using a multiband-multimode modem, not shown) such as to process digitaldata sent and received using transceivers 106, 156. In an aspect,transceivers 106, 156 can be multiband and be configured to supportmultiple frequency bands for a specific communications protocol. In anaspect, transceivers 106, 156 can be configured to support multipleoperating networks and communications protocols. Thus, for example,transceivers 106, 156 may enable transmission and/or reception ofsignals based on a specified modem configuration.

Where transmitting entity 102-a is a UE, the UE may comprise any type ofmobile device, such as, but not limited to, a smartphone, cellulartelephone, mobile phone, laptop computer, tablet computer, or otherportable networked device that can be a standalone device, tethered toanother device (e.g., a modem connected to a computer), a watch, apersonal digital assistant, a personal monitoring device, an “Internetof everything” (IoE) device, a machine monitoring device, a machine tomachine communication device, etc. In addition, a UE may also bereferred to by those skilled in the art as a mobile station, asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a mobile communications device, a wirelessdevice, a wireless communications device, a remote device, a mobilesubscriber station, an access terminal, a mobile terminal, a wirelessterminal, a remote terminal, a handset, a terminal, a user agent, amobile client, a client, or some other suitable terminology. In general,a UE may be small and light enough to be considered portable and may beconfigured to communicate wirelessly via an over-the-air communicationlink using one or more OTA communication protocols described herein.Additionally, in some examples, a UE may be configured to facilitatecommunication on multiple separate networks via multiple separatesubscriptions, multiple radio links, and/or the like.

Furthermore, where receiving entity 104 is a network entity, the networkentity may comprise one or more of any type of network module, such asan access point, a macro cell, including a base station (BS), node B,eNodeB (eNB), a relay, a peer-to-peer device, an authentication,authorization and accounting (AAA) server, a mobile switching center(MSC), a mobility management entity (MME), a radio network controller(RNC), a small cell, etc. As used herein, the term “small cell” mayrefer to an access point or to a corresponding coverage area of theaccess point, where the access point in this case has a relatively lowtransmit power or relatively small coverage as compared to, for example,the transmit power or coverage area of a macro network access point ormacro cell. For instance, a macro cell may cover a relatively largegeographic area, such as, but not limited to, several kilometers inradius. In contrast, a small cell may cover a relatively smallgeographic area, such as, but not limited to, a home, a building, or afloor of a building. As such, a small cell may include, but is notlimited to, an apparatus such as a BS, an access point, a femto node, afemtocell, a pico node, a micro node, a Node B, eNB, home Node B (HNB)or home evolved Node B (HeNB). Therefore, the term “small cell,” as usedherein, refers to a relatively low transmit power and/or a relativelysmall coverage area cell as compared to a macro cell. Additionally, anetwork entity may communicate with one or more other network entitiesof wireless and/or core networks.

Additionally, system 100 may include any network type, such as, but notlimited to, wide-area networks (WAN), wireless networks (e.g. IEEE802.11 or cellular network), the Public Switched Telephone Network(PSTN) network, ad hoc networks, personal area networks (e.g.Bluetooth®) or other combinations or permutations of network protocolsand network types. Such network(s) may include a single local areanetwork (LAN) or wide-area network (WAN), or combinations of LANs orWANs, such as the Internet. Such networks may comprise a Wideband CodeDivision Multiple Access (W-CDMA) system, and may communicate with oneor more UEs according to this standard. As those skilled in the art willreadily appreciate, various aspects described herein may be extended toother telecommunication systems, network architectures and communicationstandards. By way of example, various aspects may be extended to otherUniversal Mobile Telecommunications System (UMTS) systems such as TimeDivision Synchronous Code Division Multiple Access (TD-SCDMA), HighSpeed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access(HSUPA), High Speed Packet Access Plus (HSPA+) and Time-Division CDMA(TD-CDMA). Various aspects may also be extended to systems employingLong Term Evolution (LTE) (in frequency division duplexing (FDD), timedivision duplexing (TDD), or both modes), LTE-Advanced (LTE-A) (in FDD,TDD, or both modes), 5^(th) Generation Mobile Network (5G), CDMA2000,Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB),Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi),IEEE 802.16 (WiMAX®), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth,and/or other suitable systems. The actual telecommunication standard,network architecture, and/or communication standard employed will dependon the specific application and the overall design constraints imposedon the system. The various devices coupled to the network(s) (e.g.,transmitting entity 102-a and/or receiving entity 104) may be coupled toa core network via one or more wired or wireless connections.

FIG. 2 illustrates a method 200 for transmitting at least one modulatedsymbol from a first transmitting entity to a receiving entity. Method200 includes, optionally, at Block 202, obtaining at least one symbolfor transmitting to the receiving entity. In an aspect, input streamobtaining component 112 of the first transmitting entity 102-a, e.g., inconjunction with processor(s) 103 and/or memory 105, can obtain at leastone symbol for transmitting to receiving entity 104. For example, the atleast one symbol may be a next symbol in a sequence of symbols to bemodulated for transmission from the first transmitting entity 102-a tothe receiving entity 104.

Method 200 includes, at Block 204, identifying a first spreading codefor the first transmitting entity different from a second spreading codefor a second transmitting entity. In an aspect, spreading codedetermining component 114 of the first transmitting entity 102-a, e.g.,in conjunction with processor(s) 103 and/or memory 105, can identify thefirst spreading code. In an aspect, spreading code determining component114 can be configured to assign a set of tone locations for modulatingat least one symbol at the first transmitting entity 102-a. It is to beappreciated that the set of tone locations assigned for modulating theat least one symbol at the first transmitting entity 102-a may bedifferent from a set of tone locations assigned for modulating the atleast one symbol at the second transmitting entity 102-b. It is to befurther appreciated that the first spreading code and the secondspreading code may be configured to minimize an overlap of tones used bythe first and second transmitting entities 102-a, 102-b for modulatingthe at least one symbol. As such, in an aspect, the spreading codedetermining component 114 can identify or select the first spreadingcode and the second spreading code from a set of spreading codes (e.g.,a set of spreading codes stored in memory 105) that is configured tominimize an overlap of tones between users (e.g., first transmittingentity 102-a and second transmitting entity 102-b).

Method 200 includes, at Block 206, generating at least one modulatedsymbol by performing FSK modulation of the at least one symbol based onthe first spreading code. In an aspect, FSK encoding component 118 ofthe first transmitting entity 102-a, e.g., in conjunction withprocessor(s) 103 and/or memory 105, can modulate (e.g., encode) the atleast one symbol using FSK based on the first spreading code identifiedat, e.g., block 204. For example, in an aspect, the FSK encodingcomponent 118 can encode the at least one symbol using M-ary FSK, whereM is a value greater than or equal to two, based on the first spreadingcode.

An example is depicted in FIG. 3, where a first transmitting entity,e.g. first UE 310, and a second transmitting entity, e.g. second UE 320,encode an input stream of symbols using four FSK (4-FSK) based on afirst spreading code and a second spreading code, respectively. Each ofUE 310 and UE 320 may include or may be examples of transmittingentities 102-a and 102-b shown in FIG. 1. In an aspect, the input streamof symbols may include, for example, four symbols, e.g. symbols 302,304, 306, and 308. In this example, the first UE 310 encodes symbol 302as tone k and tone k+4. The first UE 310 encodes the next symbol 304 astone k+1 and tone k+5. The first UE 310 encodes the next symbol 306 astone k+2 and tone k+6. The first UE 310 encodes the subsequent symbol308 as tone k+3 and tone k+7. In this example, the first spreading code,that is, the tone assignment used by first UE 310, is designed such thateach symbol encoded by the first UE 310 does not overlap with a symbolencoded by the second UE 320 at more than one tone location. Forexample, the symbol 302 is encoded by the second UE 320 as tone k andtone k+5. The next symbol 304 is encoded by the second UE 320 as tonek+1 and tone k+6. The next symbol 306 is encoded by the second UE 320 astone k+2 and tone k+7. The subsequent symbol 308 is encoded by thesecond UE 320 as tone k+3 and tone k+4. In this example, each symbol isencoded by the first UE 310 and second UE 320 using a spreading factorof two (e.g., each symbol 302, 304, 306, and/or 308 is spread over twotones). It is to be appreciated that a spreading factor equal to a valuegreater than two may also be used to encode each symbol at a UE. Forexample, in an aspect, the spreading factor may equal the number of UEscommunicating with receiving entity 104.

For example, referring to FIG. 4, four transmitting entities, e.g. firstUE 410, second UE 420, third UE 430, and fourth UE 440, may eachcommunicate with receiving entity 104 and encode an input stream ofsymbols, e.g., symbols 302, 304, 306, and 308 of FIG. 3, using 4-FSKbased on a first spreading code, a second spreading code, a thirdspreading code, and a fourth spreading code, respectively. In thisexample, each of the first UE 410, second UE 420, third UE 430, andfourth UE 440 can encode each of the symbols as a first tone, secondtone, third tone, and fourth tone (e.g., the spreading factor is four).It is to be appreciated that, in this example, the spreading codes areconfigured such that any two symbols do not overlap at more than twotone locations.

Referring again to FIG. 2, method 200 further includes, at Block 210,transmitting the at least one modulated symbol to a receiving entity,e.g., receiving entity 104. In an aspect, waveform generating component116 and/or transceiver 106 of the first transmitting entity 102-a, e.g.,in conjunction with processor(s) and/or memory 105, can generate awaveform for transmitting each symbol FSK-modulated at, e.g., block 206.For example, in an aspect, transceiver 106, or a portion thereof, e.g.,in conjunction with processor(s) 103 and/or memory 105, can transmit thewaveform (e.g. signal 109-a) to the receiving entity 104.

In another aspect, QAM/PSK encoding component 130, e.g., in conjunctionwith processor(s) 103 and/or memory 105, can optionally modulate (e.g.,encode), at Block 208, each FSK-modulated symbol using QAM and/or PSKmodulation. For example, QAM/PSK encoding component 130, e.g., inconjunction with processor(s) 103 and/or memory 105, can optionallymodulate at least one tone associated with each FSK-modulated symbolusing QAM and/or PSK modulation to generate the waveform fortransmitting the FSK-modulated symbols. For example, the QAM/PSKencoding component 130 can apply different known QAM and/or PSKmodulation techniques to further modulate each tone associated with eachFSK-modulated symbol.

FIG. 5 illustrates an example method 500 for decoding (e.g.,demodulating) signals received from multiple transmitting entities(e.g., the first UE 310 and the second UE 320 illustrated in FIG. 3).Method 500 includes, at Block 502, receiving at least a first modulatedsymbol from a first UE, where the first modulated symbol is FSKmodulated based on a first spreading code. In an aspect, data streamobtaining component 122, e.g., in conjunction with processor(s) 153,memory 155, and/or transceiver 156, of the receiving entity 104 canreceive one or more modulated symbols from first UE 310 (FIG. 3). Eachof the modulated symbols can be transmitted by the first UE 310 (FIG. 3)in accordance with the waveform generation aspects described herein(e.g., by waveform generating component 116 and/or its subcomponents,using the method 200 of FIG. 2, etc.).

Method 500 includes, at Block 504, receiving at least a second modulatedsymbol from at least one second UE, where the second modulated symbol isFSK modulated based on a second spreading code. In an aspect, datastream obtaining component 122, e.g., in conjunction with processor(s)153, memory 155, and/or transceiver 156, of the receiving entity 104 canreceive one or more modulated symbols from at least one second UE (e.g.,second UE 320 (FIG. 3)). Each of the modulated symbols can betransmitted by the at least one second UE in accordance with thewaveform generation aspects described herein (e.g., by waveformgenerating component 116 and/or its subcomponents, using the method 200of FIG. 2, etc.).

Method 500 also includes, at Block 506, performing decoding of each ofthe first modulated symbol and the second modulated symbol based on thefirst spreading code and the second spreading code. In an aspect, datastream obtaining component 122, e.g., in conjunction with processor(s)153 and/or memory 155, can perform decoding of each of the firstmodulated symbol and the second modulated symbol to produce adistinguishable symbol transmitted by each of the first UE 310 (FIG. 3)and the at least one second UE (e.g., second UE 320 (FIG. 3)). That is,based on the first spreading code and the second spreading code, it ispossible to distinguish symbols transmitted by different UEs.

Block 506 may optionally include, at Block 508, decoding of each of thefirst modulated symbol and the second modulated symbol based oninformation about the channel, where at least one tone of each of thefirst modulated symbol and the second modulated symbol is further QAMand/or PSK modulated.

In an aspect, as illustrated in FIG. 6, the data stream obtainingcomponent 122 includes a FSK decoding component 124 for performing FSKdecoding of signals received from multiple transmitting entities (e.g.,first transmitting entity 102-a and second transmitting entity 102-b).In an aspect, the FSK decoding component 124 includes a multi-user FSKtone searcher 610 for detecting FSK tones received from the plurality oftransmitting entities 102-a, 102-b. The multi-user FSK tone searcher 610can distinguish FSK tones of each of the transmitting entities 102-a,102-b based on a different spreading code used by each transmittingentity 102-a, 102-b to modulate symbols. The FSK decoding component 124further includes two or more channel code decoders (e.g., a firstchannel decoder 611 and a second channel decoder 612) for decoding thedetected FSK tones to produce distinguishable decoded FSK data for eachof the plurality of transmitting entities 102-a, 102-b. Each channelcode decoder may be associated with a different wireless device (e.g., adifferent UE). For example, the first channel code decoder 611 may beassociated with a first UE, and the second channel code decoder 612 maybe associated with a second UE.

An example is depicted in FIG. 7 where a base station 710, decodes tonesreceived from the first UE 310 and the second UE 320. The base station710 may include or may be an example of the receiving entity 104 shownin FIG. 1. Each of the first UE 310 and the second UE 320 may include ormay be examples of transmitting entities 102-a and 102-b shown in FIG.1.

In an aspect, the multi-user FSK tone searcher 610 (FIG. 6) of the basestation 710 can measure the power of each FSK tone (e.g., power 720,722, 724, 726, 728, 730, 732, and 734 of tones k through k+7,respectively). In an aspect, the multi-user FSK searcher 610 (FIG. 6)can perform hard-decision or soft-decision demodulation to distinguishFSK tones of each UE (e.g., the first UE 310 and the second UE 320). Forexample, in an aspect, the multi-user FSK searcher 610 (FIG. 6) cancalculate or determine (e.g., from a table or other data array) themaximum power among |720|²+|728|², |722|²+|730|², |724|²+|732|², and|726|²+|734|², in accordance with a first spreading code used by thefirst UE 310. For example, in this aspect, the multi-user FSK searcher610 (FIG. 6) can select the combination of tone locations having themaximum power as a possible combination of tone locations used by thefirst UE 310 for performing FSK modulation. Alternatively, in anotheraspect, the multi-user FSK searcher 610 (FIG. 6) can select (e.g., froma table or other data array) all combinations of tone locationscorresponding to the first spreading code (e.g., (k, k+4), (k+1, k+5),(k+2, k+6), and (k+3, k+7)) as possible combinations of tone locationsused by the first UE 310 for performing FSK modulation. In this aspect,the multi-user FSK searcher 610 (FIG. 6) can compute a log-likelihoodratio (LLR) for each of the possible combinations of tone locationsbased on the measured power of each tone. Similarly, in an aspect, themulti-user FSK searcher 610 (FIG. 6) can calculate or determine (e.g.,from a table or other data array) the maximum power among |720|²+|730|²,|722|²+|732|², |724|²+|734|², and |726|²+|728|², in accordance with asecond spreading code used by the second UE 320. For example, in thisaspect, the multi-user FSK searcher 610 (FIG. 6) can select thecombination of tone locations having the maximum power as a possiblecombination of tone locations used by the second UE 320 for performingFSK modulation. Alternatively, in another aspect, the multi-user FSKsearcher 610 (FIG. 6) can select (e.g., from a table or other dataarray) all combinations of tone locations corresponding to the secondspreading code (e.g., (k, k+5), (k+1, k+6), (k+2, k+7), and (k+3, k+4))as possible combinations of tone locations used by the second UE 320 forperforming FSK modulation. In this aspect, the multi-user FSK searcher610 (FIG. 6) can compute a log-likelihood ratio (LLR) for each of thepossible combinations of tone locations based on the measured power ofeach tone.

The first channel code decoder 611 and the second channel code decoder612 of the base station 710 can then each decode FSK data received fromthe first UE 310 and the second UE 320, respectively. For example, in anaspect, the first channel code decoder 611 and the second channel codedecoder 612 can decode FSK data associated with the first UE 310 and thesecond UE 320, respectively, based on the combination of tone locationscalculated or determined as having the maximum power. Alternatively, inanother aspect, the first channel code decoder 611 can decode FSK dataassociated with the first UE 310 based on the computed LLRs of each ofthe combinations of tone locations corresponding to the first spreadingcode. Similarly, the second channel code decoder 612 can decode FSK dataassociated with the second UE 320 based on the computed LLRs of each ofthe combinations of tone locations corresponding to the second spreadingcode.

For example, the base station 710 can receive a first symbol encoded astone k and tone k+4 from the first UE 310 and can simultaneously receivea second symbol encoded as tone k and tone k+5 from the second UE 320.In this example, the multi-user FSK tone searcher 610 can calculate ordetermine that the maximum power corresponding to the first spreadingcode (e.g., the maximum power among |720|²+|728|², |722|²+|730|²,|724|²+|732|², and |726|²+|734|²) is |720|²+|728|². Accordingly, themulti-user FSK tone searcher 610 can select tone k and tone k+4 aspossible tone locations used by the first UE 310 for performing FSKmodulation (e.g., encoding), and the first channel code decoder 611 candecode FSK data associated with the first UE 310 based on the selectedpossible tone locations. Further, in this example, the multi-user FSKtone searcher 610 can determine that the maximum power corresponding tothe second spreading code (e.g., the maximum power among |720|²+|730|²,|722|²+|732|², |724|²+|734|², and |726|²+|728|²) is |720|²+|730|².Accordingly, the multi-user FSK tone searcher 610 can select tone k andtone k+5 as possible tone locations used by the second UE 320 forperforming FSK modulation, and the second channel code decoder 612 candecode FSK data associated with the second UE 320 based on the selectedpossible tone locations.

In an aspect, as illustrated in FIG. 6, the data stream obtainingcomponent 122 optionally includes a QAM decoding component 126 for QAM(and/or PSK) decoding (e.g., demodulating) of signals received from themultiple transmitting entities 102-a, 102-b. In an aspect, the QAMdecoding component 126 includes multiple QAM demodulators (e.g., 620 and621). Each of the QAM demodulators can receive decoded FSK data from arespective channel code decoder (e.g., 611 and 612), detect at least oneQAM (and/or PSK) modulated symbol associated with the FSK data, and sendthe at least one detected QAM (and/or PSK) symbol to a respectivechannel code decoder (e.g., 622 or 623).

For example, in an aspect, each of the QAM demodulators 620, 621 canperform hard-decision or soft-decision demodulation. For example, usinghard-decision demodulation, each of the QAM demodulators 620, 621 candetect a possible QAM (and/or PSK) symbol associated with the FSK data.Each of the QAM demodulators 620, 621 can send the detected possible QAM(and/or PSK) symbol to the respective channel code decoder 622 or 623.Alternatively, using soft-decision demodulation, each of the QAMdemodulators 620, 621 can detect multiple possible QAM (and/or PSK)symbols associated with the FSK data and compute a LLR for each of thepossible QAM (and/or PSK) symbols (e.g., by utilizing information aboutthe channel). Each of the QAM demodulators 620, 621 can send all of thedetected possible QAM (and/or PSK) symbols, as well as the computedLLRs, to the respective channel code decoder 622 or 623.

The respective channel code decoder 622 or 623 can then decode QAM(and/or PSK) data associated with each transmitting entity 102-a, 102-bbased on the detected possible QAM (and/or PSK) symbols. For example,the channel code decoders 622, 623 can decode QAM (and/or PSK) dataassociated with transmitting entity 102-a and transmitting entity 102-b,respectively, based on the computed LLRs of the detected possible QAM(and/or PSK) symbols.

FIG. 8 is a block diagram of an embodiment of a base station 810 and aUE 850 in a MIMO system 800. For example, base station 810 may include areceiving entity 104, and/or one or more components thereof, such as acommunicating component 120, as described herein. Similarly, UE 850 mayinclude a transmitting entity 102-a, and/or one or more componentsthereof, such as a communicating component 110, as described herein. Atthe base station 810, traffic data for a number of data streams isprovided from a data source 812 to a transmit (TX) data processor 814.

In an embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 814 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., FSK, QAM, and/or PSK) selectedfor that data stream to provide modulation symbols. The data rate,coding, and modulation for each data stream may be determined byinstructions performed by processor 830.

The modulation symbols for all data streams are then provided to a TXMIMO processor 820, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 820 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 822 a through 822 t. Incertain embodiments, TX MIMO processor 820 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 822 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 822 a through 822 t are thentransmitted from N_(T) antennas 824 a through 824 t, respectively.

At UE 850, the transmitted modulated signals are received by N_(R)antennas 852 a through 852 r and the received signal from each antenna852 is provided to a respective receiver (RCVR) 854 a through 854 r.Each receiver 854 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 860 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 854 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 860 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 860 is complementary to thatperformed by TX MIMO processor 820 and TX data processor 814 at basestation 810.

A processor 870 periodically determines which pre-coding matrix to use(discussed below). Processor 870 formulates a reverse link messagecomprising a matrix index portion and a rank value portion. Processor870 is additionally coupled to a memory 872 that may store instructions,parameters, and/or other data related to executing functions describedherein (e.g., function of communicating component 110).

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 838, whichalso receives traffic data for a number of data streams from a datasource 836, modulated by a modulator 880, conditioned by transmitters854 a through 854 r, and transmitted back to base station 810.

At base station 810, the modulated signals from UE 850 are received byantennas 824, conditioned by receivers 822, demodulated by a demodulator840, and processed by a RX data processor 842 to extract the reservelink message transmitted by the UE 850. Processor 830 then determineswhich pre-coding matrix to use for determining the beamforming weightsthen processes the extracted message. Processor 830 is additionallycoupled to a memory 832 that may store instructions, parameters, and/orother data related to executing functions described herein (e.g.,function of communicating component 120).

Several aspects of a telecommunications system have been presented withreference to a W-CDMA system. As those skilled in the art will readilyappreciate, various aspects described herein may be extended to othertelecommunication systems, network architectures and communicationstandards.

By way of example, various aspects described herein may be extended toother UMTS systems such as W-CDMA, TD-SCDMA, High Speed Downlink PacketAccess (HSDPA), High Speed Uplink Packet Access (HSUPA), High SpeedPacket Access Plus (HSPA+) and TD-CDMA. Various aspects may also beextended to systems employing Long Term Evolution (LTE) (in FDD, TDD, orboth modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes),CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband(UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. Theactual telecommunication standard, network architecture, and/orcommunication standard employed will depend on the specific applicationand the overall design constraints imposed on the system.

In accordance with various aspects described herein, an element, or anyportion of an element, or any combination of elements may be implementedwith a “processing system” that includes one or more processors (seee.g., FIG. 1). Examples of processors include microprocessors,microcontrollers, graphics processing units (GPUs), central processingunits (CPUs), application processors, digital signal processors (DSPs),reduced instruction set computing (RISC) processors, system-on-a-chip(SoC), baseband processors, field programmable gate arrays (FPGAs),programmable logic devices (PLDs), state machines, gated logic, discretehardware circuits, and other suitable hardware configured to perform thevarious functionality described herein. One or more processors in theprocessing system may execute software. Software shall be construedbroadly to mean instructions, instruction sets, code, code segments,program code, programs, subprograms, software modules, applications,software applications, software packages, routines, subroutines,objects, executables, threads of execution, procedures, functions, etc.,whether referred to as software, firmware, middleware, microcode,hardware description language, or otherwise. The software may reside ona computer-readable medium. The computer-readable medium may be anon-transitory computer-readable medium. A non-transitorycomputer-readable medium includes, by way of example, a magnetic storagedevice (e.g., hard disk, floppy disk, magnetic strip), an optical disk(e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, aflash memory device (e.g., card, stick, key drive), random access memory(RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM(EPROM), electrically erasable PROM (EEPROM), a register, a removabledisk, and any other suitable medium for storing software and/orinstructions that may be accessed and read by a computer. Thecomputer-readable medium may also include, by way of example, a carrierwave, a transmission line, and any other suitable medium fortransmitting software and/or instructions that may be accessed and readby a computer. The computer-readable medium may be resident in theprocessing system, external to the processing system, or distributedacross multiple entities including the processing system. Thecomputer-readable medium may be embodied in a computer-program product.By way of example, a computer-program product may include acomputer-readable medium in packaging materials. Those skilled in theart will recognize how best to implement the functionality describedherein depending on the particular application and the overall designconstraints imposed on the overall system.

It is to be understood that the specific order or hierarchy of steps inthe methods disclosed is an illustration of exemplary processes. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the methods or methodologies described herein maybe rearranged. The accompanying method claims present elements of thevarious steps in a sample order, and are not meant to be limited to thespecific order or hierarchy presented unless specifically recitedtherein.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, band c. All structural and functional equivalents to the elements of thevarious aspects described herein that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. No claim element is to be construed under the provisions of35 U.S.C. §112(f) unless the element is expressly recited using thephrase “means for” or, in the case of a method claim, the element isrecited using the phrase “step for.”

What is claimed is:
 1. A method of multi-user wireless communications,comprising: receiving, via a channel, a first modulated symbol from afirst user equipment (UE), the first modulated symbol beingfrequency-shift keying (FSK) modulated based on a first spreading code;receiving, via the channel, a second modulated symbol from at least onesecond UE, the second modulated symbol being FSK modulated based on asecond spreading code different from the first spreading code; anddecoding, based on the first spreading code and the second spreadingcode, each of the first modulated symbol and the second modulated symbolto produce a distinguishable symbol transmitted by each of the first UEand the at least one second UE.
 2. The method of claim 1, wherein: atleast one tone of each of the first modulated symbol and the secondmodulated symbol is further quadrature amplitude modulation (QAM) orphase-shift keying (PSK) modulated, and the decoding of each of thefirst modulated symbol and the second modulated symbol is further basedon information about the channel.
 3. The method of claim 1, wherein: thefirst spreading code corresponds to a first location assignment fortones in the first modulated symbol, and the second spreading codecorresponds to a second location assignment for tones in the secondmodulated symbol, the second location assignment being different fromthe first location assignment.
 4. The method of claim 3, wherein: thefirst modulated symbol having at least one repeated symbol, tonelocations for each repeated symbol of the first modulated symbol beingassigned according to the first location assignment, and the secondmodulated symbol having at least one repeated symbol, tone locations foreach repeated symbol of the second modulated symbol being assignedaccording to the second location assignment.
 5. The method of claim 3,wherein the first location assignment and the second location assignmentare configured to minimize tone overlap between the first modulatedsymbol and the second modulated symbol.
 6. The method of claim 1,wherein the first modulated symbol and the second modulated symbol areM-ary FSK modulated, where M is greater than
 2. 7. The method of claim1, wherein the decoding comprises: determining a power for each toneassociated with the first modulated symbol and the second modulatedsymbol; identifying the distinguishable symbol transmitted by the firstUE based on the power of each tone and the first spreading code; andidentifying the distinguishable symbol transmitted by the at least onesecond UE based on the power of each tone and the second spreading code.8. The method of claim 1, wherein: at least one tone of each of thefirst modulated symbol and the second modulated symbol is further QAM orPSK modulated, and the decoding includes: a first decoding of the firstmodulated symbol and the second modulated symbol to produce FSK decodeddata; and a second decoding, based on the FSK decoded data and theinformation about the channel, of the first modulated symbol and thesecond modulated symbol to produce the distinguishable symboltransmitted by each of the first UE and the at least one second UE. 9.An apparatus for multi-user wireless communications, comprising: atransceiver; a memory configured to store instructions; and one or moreprocessors communicatively coupled to the transceiver and the memory,the one or more processors configured to execute the instructions to:receive, via the transceiver and a channel, a first modulated symbolfrom a first user equipment (UE), the first modulated symbol beingfrequency-shift keying (FSK) modulated based on a first spreading code;receive, via the transceiver and the channel, a second modulated symbolfrom at least one second UE, the second modulated symbol being FSKmodulated based on a second spreading code different from the firstspreading code; and decode, based on the first spreading code and thesecond spreading code, each of the first modulated symbol and the secondmodulated symbol to produce a distinguishable symbol transmitted by eachof the first UE and the at least one second UE.
 10. The apparatus ofclaim 9, wherein: at least one tone of each of the first modulatedsymbol and the second modulated symbol is further quadrature amplitudemodulation (QAM) or phase-shift keying (PSK) modulated, and the decodingof each of the first modulated symbol and the second modulated symbol isfurther based on information about the channel.
 11. The apparatus ofclaim 9, wherein: the first spreading code corresponds to a firstlocation assignment for tones in the first modulated symbol, and thesecond spreading code corresponds to a second location assignment fortones in the second modulated symbol, the second location assignmentbeing different from the first location assignment.
 12. The apparatus ofclaim 11, wherein: the first modulated symbol having at least onerepeated symbol, tone locations for each repeated symbol of the firstmodulated symbol being assigned according to the first locationassignment, and the second modulated symbol having at least one repeatedsymbol, tone locations for each repeated symbol of the second modulatedsymbol being assigned according to the second location assignment. 13.The apparatus of claim 11, wherein the first location assignment and thesecond location assignment are configured to minimize tone overlapbetween the first modulated symbol and the second modulated symbol. 14.The apparatus of claim 9, wherein the first modulated symbol and thesecond modulated symbol are M-ary FSK modulated, where M is greater than2.
 15. The apparatus of claim 9, wherein to decode each of the firstmodulated symbol and the second modulated symbol, the one or moreprocessors are further configured to: determine a power for each toneassociated with the first modulated symbol and the second modulatedsymbol; identify the distinguishable symbol transmitted by the first UEbased on the power of each tone and the first spreading code; andidentify the distinguishable symbol transmitted by the at least onesecond UE based on the power of each tone and the second spreading code.16. The apparatus of claim 9, wherein: at least one tone of each of thefirst modulated symbol and the second modulated symbol is further QAM orPSK modulated, and the decoding includes: a first decoding of the firstmodulated symbol and the second modulated symbol to produce FSK decodeddata; and a second decoding, based on the FSK decoded data and theinformation about the channel, of the first modulated symbol and thesecond modulated symbol to produce the distinguishable symboltransmitted by each of the first UE and the at least one second UE. 17.An apparatus for multi-user wireless communications, comprising: meansfor receiving, via a channel, a first modulated symbol from a first userequipment (UE), the first modulated symbol being frequency-shift keying(FSK) modulated based on a first spreading code, the means further forreceiving, via the channel, a second modulated symbol from at least onesecond UE, the second modulated symbol being FSK modulated based on asecond spreading code different from the first spreading code; and meansfor decoding, based on the first spreading code and the second spreadingcode, each of the first modulated symbol and the second modulated symbolto produce a distinguishable symbol transmitted by each of the first UEand the at least one second UE.
 18. A method of multi-user wirelesscommunications, comprising: identifying, at a first UE, a firstspreading code different from a second spreading code for a second UE;generating, by the first UE, at least one first modulated symbol byperforming frequency-shift keying (FSK) modulation of at least one firstsymbol based on the first spreading code; and transmitting the at leastone first modulated symbol to a base station, the base station beingconfigured to produce, based on the first spreading code, the at leastone first symbol from the at least one first modulated symboldistinguishable from at least one second symbol produced by the basestation for the second UE from at least one second modulated symboltransmitted by the second UE.
 19. The method of claim 18, whereingenerating the at least one first modulated symbol further comprises:performing quadrature amplitude modulation (QAM) or phase-shift keying(PSK) modulation of at least one tone of the at least one firstmodulated symbol.
 20. The method of claim 18, wherein the firstspreading code corresponds to a first location assignment for tones inthe first modulated symbol.
 21. The method of claim 20, wherein thesecond spreading code corresponds to a second location assignment fortones in the second modulated symbol, the second location assignmentbeing different from the first location assignment.
 22. The method ofclaim 20, wherein generating the at least one first modulated symbolfurther comprises: assigning the at least one first symbol to aplurality of tone locations according to the first location assignment.23. The method of claim 18, wherein the FSK modulation comprises M-aryFSK modulation, and wherein M is greater than 2.